This invention relates to compositions and methods of making pultruded fiberglass sign panels, in particular, a pultruded fiberglass sign panel having an overall and cross-section designs that are useful for replacing aluminum allow highway signs. The compositions and methods of the current invention produce lighter, stronger, less expansion and contraction, and less expensive sign panels when compared to similar extruded aluminum sign panels, steel panels, or wood sign panels. Additionally, a fiberglass reinforced polymer material that useful for making sign panels can be made from recycled or virgin materials.
Highway Signs. The United States has over 6.3 million kilometers (“km”) of highways crisscrossing the nation's landscape. This number includes about 4.1 million km of paved roads (including 74,406 km of expressways) and about 2.2 million km of unpaved roads. Information signage is located on nearly every kilometer of this immense network of roads, as well as roads in countries around the globe.
Many years ago, the material of choice that was used for highway signage in the United States was wood. However, since the mid 1960's, there has been a shift in the use of signage material toward the current standard of aluminum. This shift was due primarily because an aluminum sign has many superior qualities when compared to a similarly sized wood sign, including increased strength, decreased weight, and longer durability. In contrast, the disadvantages to aluminum signage is the variable cost of aluminum material itself, and the increasing cost of alodizing the aluminum alloys to increase their corrosion resistance and to improve their paint bonding qualities. For example, since 2002, the cost of aluminum has increased about 60% and the cost of Alodizing aluminum has increased more than 25%. Furthermore, aluminum has little or no resistance to impact deformation. There is a need in the highway sign industry to replacement aluminum as a choice material.
Fiberglass reinforced polymers (“FRP”) are primarily made from glass and resin. Because the glass component can be made from sand or recycled glass, FRP is a much cheaper raw material than typical aluminum alloys. Additionally, a finished sign made from FRP requires fewer processing steps when compared to signs made from aluminum, which further reduces the cost of sign manufacturing.
Recycled Glass. Glass recycling has been around in the United States since glass has been used in the manufacturing of containers; for almost 100 years. Glass is one of the easiest commodities to recycle and there are many of different uses for it. In the early days and up until recently, glass bottles were returned to the company and cleaned for re-use. Today the majority of glass that is recycled is crushed and used to manufacture new containers or fiberglass insulation, as well as other secondary uses that are developing quickly.
Pultrusion. Generally, the pultrusion process is a material production process that uses continuous fiber reinforcement in roving or mat forms. The roving forms are drawn through a resin bath to coat each fiber with a resin mixture. The coated fibers are then drawn through a heated die. The cross-sectional shape of the pultrusion can be made into nearly any type of simple or complex shape, provided that the shape has a continuous cross sectional area. Cure of thermosetting resin is initiated by heat in the die and catalyst in the resin mix. The rate of reaction is controlled by heating and cooling zones in the die. The resulting high strength profile is cut to length, and typically ready to use as it leaves the pultrusion machine.
Several United States Patents, such as, U.S. Pat. Nos. 6,872,273; 4,559,262; U.S. Pat. No. 4,394,338; U.S. Pat. No. 4,540,737; and U.S. Pat. No. 4,541,884 describe in detail several known pultruding techniques, each of these patents are specifically incorporated by reference herein. More specifically, U.S. Pat. No. 4,559,262, issued to Cogswell, et al., on Dec. 17, 1985, titled “Fibre Reinforced Compositions and Methods for Producing such Compositions,” (“the '262 Patent”) discloses fibre-reinforced structures comprising a thermoplastics polymer and containing at least 30% by volume of reinforcing filaments extending longitudinally of the structure which have been produced in a continuous process and which have exceptionally high stiffness. The exceptionally high stiffness is a result of thorough wetting of the reinforcing filaments by molten polymer in the continuous process. The thorough wetting gives rise to a product which can be further processed even in vigorous mixing processes such as injection molding with surprisingly high retention of the fibre length in the fabricated article. The continuous processes for producing the reinforced structures employ thermoplastics polymers having lower melt viscosities than conventionally considered suitable for achieving satisfactory physical properties.
U.S. Pat. No. 4,394,338 issued to Fuwa on Jul. 19, 1983, titled “Production of Elongated Fiber-Reinforced Composite Articles,” (“the '338 Patent”) describes the pultrusion of a fiber-reinforced plastic, an elongated fiber material impregnated with a thermosetting resin prior to setting is introduced into a long-land die, in which a thermoplastic resin and a lubricant are successively applied onto the outer surface of the impregnated fiber material thereby to make possible smooth drawing of the material through the die. As a result, the thermosetting resin is substantially set within the die, and, moreover, an elongated, fiber-reinforced, plastic composite article is produced at a reasonable speed.
U.S. Pat. No. 4,540,737 issued to Wissbrun, et al., on Sep. 10, 1985, titled “Method for the Formation of Composite Articles Comprised of Thermotropic Liquid Crystalline Polymers and Articles Produced Thereby,” (the '737 Patent”) describes a method for the production of composite articles by pultrusion is provided wherein the articles comprise thermotropic liquid crystalline polymers and reinforcing fibers. The liquid crystalline polymers employed exhibit physical characteristics such that the negative slope of a dynamic viscosity-frequency curve (as defined) is less than about 0.35. The use of polymers having such rheological characteristics enables a composite material to be produced by pultrusion in which the polymer is uniformly dispersed among the reinforcing fibers.
U.S. Pat. No. 4,541,884, issued to Cogswell, et al., on Sep. 17, 1985, titled “Method of producing fibre-reinforced composition,” (“the '884 Patent”) describes a process of producing a fibre-reinforced composition comprising drawing a plurality of continuous filaments through a melt comprising a mixture of a thermoplastic polymer and a plasticizer for the polymer in the weight ratio between 1:4 and 99:1 of polymer to plasticizer, preferably in the weight ratio 1:1 to 19:1, the plasticizer being thermally stable at least up to the temperature of the melt and having volatility characteristics such that the plasticizer can be volatilized from the composition below the decomposition temperature of the composition but has a sufficiently low volatility at the temperature of the melt to plasticize the polymer in the melt and give a melt of reduced viscosity compared with the melt viscosity of the polymer alone. The process enables higher molecular polymers to be used in the pultrusion process and enables higher fibre contents to be achieved.
U.S. Pat. No. 6,796,097, issued to Fensel, et al., on Sep. 28, 2004, titled “Roof or Wall Panel System and Method of Installation,” (“the '097 Patent”) describes a light-weight structural system consisting of a panel system having at least one pair of adjacent panels and a clip positioned between the adjacent panels. A groove or channel in each panel receives an outwardly-extending tongue or tab on the clip. Built-up gussets on the panels above and below the groove or channel provide structural strength. Upwardly-extending support members on the clip bear weight from the panels. A base section of the clip allows the clip to be fixed to a roof or wall substructure. The panels can be formed from thermosetting or thermoplastic polymers, especially fiber-reinforced polymers.
U.S. Pat. No. 6,872,273, issued to Davies, et al., on Mar. 29, 2005, titled “Method of Making a Pultruded Part with a Reinforcing Mat,” (“the '273 Patent”) describes a method of making a pultruded part having a uniform cross-section using a novel reinforcing mat. The method comprises orienting a plurality of longitudinal rovings along a longitudinal axis of a pultrusion die; providing a reinforcing structure comprising a permeable transport web of staple fibers attached to a plurality of first reinforcing fibers oriented so that the portion of the first reinforcing fibers oriented in a direction transverse to the longitudinal axis comprises at least 40% of a volume of materials comprising the reinforcing structure; shaping the reinforcing structure to generally conform with a profile of the pultrusion die; combining a resin matrix with the longitudinal rovings and the reinforcing structure in the pultrusion die so that the longitudinal rovings and the reinforcing structure are substantially surrounded by the resin matrix; at least partially curing the resin matrix in the pultrusion die; and pulling the pultruded part from the pultrusion die.
Sign Blanks. One or more of the described fiberglass pultruded panels can be assembled together and used as sign blanks. Sign blanks are employed as the supportive backing for many different types of highway signs. Of particular interest are sign blanks that are so large that they must be formed from multiple sign blank panels. Most commonly, these large sign blanks are constructed to be employed as the backing for the large information signs used along or over highways and other roads for identifying the roads, their destinations, upcoming junctions, exits, etc, see FIG. 1. In order to construct a properly sized sign blank to receive a designated sign, sign blanks are formed from multiple aluminum sign blank panels that are bolted, riveted, or otherwise secured to each other through suitable fasteners separate and distinct from the panels themselves. The information of a sign is typically adhered to the surface of the sign blank, see FIG. 2C. Aluminum is typically used because of its light weight and weather resistance, however, the cost of processing an aluminum sign blank has continued to increase. Additionally, assembled sign blanks should have a mounting or fastening means to connect the finished information sign to a sign post. Sign panels produced form FRP are stronger, longer lasting, and cheaper to produce than the current aluminum alloy sign panels.